1. Field of the Invention
This invention relates to a camera provided with means for effecting magnetic recording and reproduction on film having a magnetic recording portion which is inserted in the camera.
2. Related Background Art
Heretofore, a reading circuit for effecting reproduction on a magnetic recording medium by the use of a magnetic head has been constructed as shown in FIG. 25 of the accompanying drawings. The reference numeral 601 designates a magnetic head, the reference numeral 602 denotes a differential amplifier for amplifying the output of the magnetic head 601, and the reference numerals 603,604, 605, 606 and 607 designate resistors. The reference numerals 608 and 609 denote comparators connected to the differential amplifier 602, and the reference numeral 610 designates an RS flip-flop connected to the comparators 608 and 609.
The resistors 603, 604, 605, 606 and 607 supply the input bias current of the differential amplifier 602. The resistor 607 is a gain setting resistor. When the value of the resistor 607 is determined, the differential voltage gain is determined as shown in FIG. 27 of the accompanying drawings, and the reproducing signal output of the magnetic head 601 conforming to the voltage amplification degree thereof is output.
FIG. 26 of the accompanying drawings diagrammatically shows an amplifying circuit for amplifying the reproducing signal of the magnetic head. In the circuit of FIG. 26, the gain setting resistor 607 is connected to terminals (b) and (g), and the output of the magnetic head 601 is connected to terminals (a) and (h). Tr1-Tr13 designate transistors. When a potential difference occurs between terminals (a) and (g), a difference occurs between electric currents flowing to the transistors Tr1 and Tr2. The current difference is converted into a potential difference by the transistors Tr3-Tr6 which constitute the feedback circuit of the subsequent stage. The conversion rate of the current difference and the potential difference is varied by the value of the resistor 607. Accordingly, when the value of the resistor 607 is determined, the differential voltage gain is determined as shown in FIG. 27, and the reproducing signal output of the magnetic head conforming to the voltage amplification degree thereof is output.
In the above-described prior art, however, as shown in FIG. 27, the amplification degree is changed by a variation in the value of the resistor 607 by a temperature change or the like and therefore, the amplitude of a noise voltage applied to the comparators 608 and 609 varies, and when that amplitude becomes great, the comparators 608 and 609 are operated by the noise voltage, and this has led to the disadvantage that a wrong signal is output from the RS flip-flop circuit 610. Also, when the differential voltage gain is amplified to a frequency higher than the signal frequency from the magnetic head, it becomes a high frequency noise, and this has sometimes led to the aggravation of the signal to noise ratio.